Fluctuating restoration of <i>Suaeda</i> species in Coastal China: remote sensing-based spatiotemporal patterns and underlying drivers

Suaeda species in coastal zones play a crucial ecological role in improving saline-alkali soils and supporting habitats for migratory waterbirds. However, these ecosystems have faced sustained degradation in recent decades, especially in developing countries such as China. Since the implementation of the Sustainable Development Goals (SDGs) and integrated coastal management, the ecological importance of Suaeda species has been increasingly emphasized in restoration efforts. However, the recovery trajectory and driving mechanisms remain unclear. To address this gap, we mapped Suaeda distributions for 2016, 2020, and 2024, and analyzed the factors influencing its spatial distribution and changes. Overall accuracies for Suaeda species distribution exceeded 87%. From 2016 to 2024, the area covered by Suaeda species in coastal China increased from 64.83 km2 to 99.5 km2, demonstrating an overall upward trend with fluctuations, which reflects spatial heterogeneity and dynamic local colonization-disappearance processes. We found the spatial distribution was determined by relatively stable mean environmental factors, including soil electrical conductivity, annual mean temperature, sea surface salinity, and evapotranspiration during germination. We further discovered that temporal changes were driven by extreme environmental factors and human activities: negatively associated with Spartina alterniflora invasion, aquaculture expansion, and maximum sea surface salinity, but positively with minimum tidal levels. These findings underscore the role of S. alterniflora removal and aquaculture pond retreat strategies in facilitating Suaeda species restoration. As a case of global coastal governance, this study shows that pioneer community recovery is neither stable nor linear, highlighting the need to evaluate restoration beyond simple changes in community extent.